This invention relates to a method and apparatus for regenerating frying and cooking oils. More particularly, this invention relates to the use of electrochemical reduction for on-site regeneration of frying and cooking oils.
Frying is a process in which food is placed in a bed of cooking oil at a temperature in the range of about 300° F. to about 500° F. During the process, the food is subjected to simultaneous heat and mass transfer, accompanied by numerous chemical reactions. Frying processes may be carried out in homes, restaurants, food services and in industrial fryers. Large scale production is carried out in industrial fryers for wholesale and retail distribution of fried food. Restaurant or food service providers typically use relatively small batch fryers in which the oil content may range from about 50 pounds to about 120 pounds. Industrial fryers, also sometimes referred to as kettle fryers, are larger in size and may be batch or continuous in operation. The oil in both batch and continuous fryers may be heated either directly or indirectly and is typically continuously circulated through a filter.
During the frying process, the cooking oil undergoes several reactions. The most common reactions are hydrolysis, which is the reaction of water released from the fried food with the cooking oil, resulting in the formation of free fatty acids, autoxidation, which generates peroxides, and polymerization, which forms long carbon chain organic polymers.
The rate of hydrolysis and corresponding formation of free fatty acids depends on several factors and determines when the cooking oil, also sometimes referred to herein as frying oil, needs to be replaced. These factors include the amount of water in the fried food or added during processing of the food, the temperature at which the food is fried, and the rate of oil replacement. Generally, in order to reduce or eliminate the formation of free fatty acid due to hydrolysis, two methods are employed—the use of an inhibitor, such as polysaccharides and dietary fibers for the chemical reaction of oil hydrolysis or the use of a scavenger, such as butylated hydroxy anisole (BHA), propyl gallate, and aminoguanidine, that collects the free fatty acids as they are formed. However, neither of these methods can regenerate the cooking oil or extend the lifetime of the cooking oil during frying.
In new cooking oil as received, some free radicals, primarily from unsaturated oil, are present. The free radicals in the presence of oxygen and water initiate chain reactions to produce hydroperoxide which can affect the flavor of the food. In addition, the free radicals initiate undesirable polymerization reactions at high temperatures.